1. Field of the Invention
This invention relates to an improved semiconductive light-emitting device comprising a light-emitting layer having a strained multi-quantum well or strain compensation type multilayer quantum well structure and a light emission wavelength between 1.30 and 1.65 .mu.m.
2. Background of the Invention
Semiconductor light-emitting device comprising a light-emitting layer having a strained multilayer quantum well or strain compensation type multilayer quantum well structure and a light emission wavelength band between 1.30 and 1.65 .mu.m are well known. The light-emitting layer is constituted of quantum well layers and barrier layers and each of the quantum well layers and barrier layers is made of GaInAs or GaInAsP. The upper and lower optical confining layers are respectively arranged on and beneath the light-emitting layer to sandwich it. A pair of InP cladding layers are disposed respectively on and beneath the upper and lower optical confining layers.
While a bulk crystal structure has been traditionally used for the light-emitting layer of a semiconductive light-emitting device, it has been replaced more often than one by a multilayer quantum well or strained quantum well structure in recent years. An improved differential gain is available if a multilayer quantum well structure is used for the light emitting layer because of the stepped state density specific to such a structure. An even more improved differential gain is achievable if a strained quantum well structure is used for the light-emitting layer because of an improved symmetry and a reduced state density of the valence band. As is well known in this technical field, the differential gain is a factor that vitally affects the characteristics of laser including the maximum modulation frequency and the relative intensity noise as well as the chirping and the emission spectrum width, if the laser is a distributed feedback type semiconductive.